Trans service and trans temp expectations/max safe.

[AH64ID]

You wont find me running 4wd on the pavement. Even the standard tire pressure differences front to rear are enough to cause binding in the transfer case.

 

[transe]

1) I always thought it was hard on the drivetrain to run 4 low on dry pavement. But there was a guy with a 35 ft 5 er at Roan Mtn State Park (2012 CTD 2500)who said to get up the paved 12-15% grade, he puts it in 4 low and lets it idle up the hill.
He has the 68rfe. So, I guess I've been a bit too worried about short stints of 4x4 on dry pavement.
I did end up using 4x4 to back the travel trailer into tight spots up a steep uncline after first letting my clutch slip a bit too much. So steep, I was spinning rear wheels on dry pavement with limited slip differential.

2) When driving my dad's RV, I often shifted to neutral at stop lights. But the jolt is big on a 4.28 rear end when shifting back into gear. I guess the drivevtrain is made to withstand jolts. But was concerned about the increased number of jolts you get when shifting at stop lights. Seems like the increased number of jolts might put undue stress on u joints?

1) You are correct that 4 LOW is not recommended for on-pavement use. But that is primarily concerning the "crow hop" you get when performing a tight turn on dry pavement (with no front-to-rear differential). Driving straight forward should not cause any issues, other than some increased tire wear (the tires will slip before any "bind-up" torque in the driveline gets high enough to break something). So yes, you normally wouldn't use 4LO on pavement. But if I have to choose between an overheated trans and using 4LO for a short period, I'll choose 4LO.

2) Jolts during N-D engagement can be annoying, but they should not damage anything. The driveline torque during an N-D engagement is much less than in normal driving. The jolt/clunk is due more to backlash in the driveline than to the torque level. In normal driving, you can leave it in Drive at stop lights. But if you get into a stretch of stop-and-go during hot weather, I would start shifting it to Neutral.

 

[BaldwinScott]

I was always told that the Trans. pump does not pump fluid when it is shifted into neutral, is that true or false?

 

[transe]

I was always told that the Trans. pump does not pump fluid when it is shifted into neutral, is that true or false?

For the RFE transmissions, it is false. Line pressure is maintained (although possibly at a lower value) when in Park or Neutral.

 

[BaldwinScott]

TransEngineer: Thanks for the great info you are providing here. Learning a lot and dispelling a few myths also.